regmap: Add functions to check for access on registers

We're going to be using these in quite a few places so factor out the
readable/writable/volatile/precious checks.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index d74d306..fa2bd89 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -20,6 +20,50 @@
 
 #include "internal.h"
 
+bool regmap_writeable(struct regmap *map, unsigned int reg)
+{
+	if (map->max_register && reg > map->max_register)
+		return false;
+
+	if (map->writeable_reg)
+		return map->writeable_reg(map->dev, reg);
+
+	return true;
+}
+
+bool regmap_readable(struct regmap *map, unsigned int reg)
+{
+	if (map->max_register && reg > map->max_register)
+		return false;
+
+	if (map->readable_reg)
+		return map->readable_reg(map->dev, reg);
+
+	return true;
+}
+
+bool regmap_volatile(struct regmap *map, unsigned int reg)
+{
+	if (map->max_register && reg > map->max_register)
+		return false;
+
+	if (map->volatile_reg)
+		return map->volatile_reg(map->dev, reg);
+
+	return true;
+}
+
+bool regmap_precious(struct regmap *map, unsigned int reg)
+{
+	if (map->max_register && reg > map->max_register)
+		return false;
+
+	if (map->precious_reg)
+		return map->precious_reg(map->dev, reg);
+
+	return false;
+}
+
 static void regmap_format_4_12_write(struct regmap *map,
 				     unsigned int reg, unsigned int val)
 {